Association of Outcomes of Spinal Cord Stimulation for Chronic Low Back Pain and Psoas Measurements Based on Size of Iliopsoas Muscles

INTRODUCTION Patients experience variable long-term improvement in chronic back pain despite successful spinal cord stimulation (SCS) trials. Iliopsoas (IP) size has been shown to differ between patients with low back pain and healthy controls. In this study, we examine whether IP muscle cross-sectional area (CSA) is associated with SCS outcomes. MATERIALS AND METHODS We examined patients for whom we had lumbar MRIs 6.3 years prior to SCS and had baseline and one-year outcome data. Percent change from baseline to one year was calculated for Numeric Rating Scale (NRS), Oswestry Disability Index (ODI), Beck Depression Inventory (BDI), Pain Catastrophizing Scale (PCS), and McGill Pain Questionnaire (MPQ). Correlations between IP muscle CSA, ratio of iliopsoas muscle size to the vertebral body area (P/VBA), and the ratio of iliopsoas muscle size to BMI (P/BMI) were examined. Sex differences were considered. RESULTS A total of 73 subjects were included in this study including 30 females and 43 males. Males had significantly larger IP (males 15.70 ± 0.58, females 9.72 ± 0.43; p